Chapter 53
Community Ecology
Teaching Objectives
Interspecific Interactions and Community Structure
1. List the categories of interspecific interactions and explain how each interaction may affect the population densities of the two species involved.
2. State the competitive exclusion principle.
3. Define an ecological niche and restate the competitive exclusion principle using the niche concept.
4. Distinguish between fundamental and realized niche.
5. Explain how interspecific competition may lead to resource partitioning.
6. Define and compare predation, herbivory, and parasitism.
7. Give specific examples of adaptations of predators and prey.
8. Explain how cryptic coloration and warning coloration may aid an animal in avoiding predators.
9. Distinguish between Batesian mimicry and Müllerian mimicry.
10. Describe how predators may use mimicry to obtain prey.
11. Distinguish among endoparasites, ectoparasites, and parisitoids.
12. Distinguish among parasitism, mutualism, and commensalism.
13. Explain the relationship between species richness and relative abundance and explain how both contribute to species diversity.
14. Distinguish between a food chain and a food web.
15. Describe two ways to simplify food webs.
16. Summarize two hypotheses that explain why food chains are relatively short.
17. Explain how dominant and keystone species exert strong control on community structure. Describe an example of each.
18. Describe and distinguish between the bottom-up and top-down models of community organization. Describe possible features of a model that is intermediate between these two extremes.
Disturbance and Community Structure
19. Define stability and disturbance.
20. Provide examples of how disturbance may increase or decrease species diversity.
21. Give examples of humans as widespread agents of disturbance.
22. Distinguish between primary and secondary succession.
23. Describe how species that arrive early in succession may facilitate, inhibit, or tolerate later arrivals.
24. Explain why species richness declines along an equatorial-polar gradient.
25. Explain the significance of measures of evapotranspiration to species richness.
Biogeographic Factors Affect Community Biodiversity
26. Define the species-area curve.
27. Explain how species richness on islands varies according to island size and distance from the mainland.
28. Define and contrast the following pairs of hypotheses:
a. interactive hypothesis versus individualistic hypothesis
b. rivet model versus redundancy model
Student Misconceptions
1. Many students do not fully appreciate the complexity of interactions between populations in a food web. Some students do not understand the link between population growth and environmental constraints and think of populations as essentially independent. Other students recognize the importance of direct interactions between species that interact as predators and prey, but do not recognize that changes in abundance of species also impact other species that do not directly interact with them. Use examples of successful biomanipulation to illustrate that indirect effects may be as important as direct interactions in a food web.
2. Clarify to students that competition may lead to extinction of local populations but may also be an important factor in speciation as species partition resources by modifying their functional niches.
3. Students may have an exaggerated respect for the “balance of nature” and may think that a community maintains a stable and relatively constant composition of species despite disturbance. Clarify to your students that communities are not necessarily stable or static, and that change in community structure following disturbance is a natural event. Small-scale or moderate levels of disturbance may play an important role in maintaining or enhancing species diversity in a healthy community.
Further Reading
D’Avanzo, C. 2003. Research on learning: potential for improving college ecology teaching. Front Ecol Environ 1(10): 533–540.
Munson, B. H. 1994. Ecological misconceptions. Journal of Environmental Education 25(4): 30–34.
Odum, E. P. 1992. Great ideas in ecology for the 1990s. BioScience 42(7): 542–545.
Chapter Guide to Teaching Resources
Overview: What is a community?
Concept 53.1A community’s interactions include competition, predation, herbivory, symbiosis, and disease
Transparencies
Figure 53.2 Can a species’ niche be influenced by interspecific competition?
Figure 53.3 Resource partitioning among Dominican Republic lizards
Figure 53.4 Character displacement: Indirect evidence of past competition
Instructor and Student Media Resources
Video: Whale eating a seal
Video: Clownfish and anemone
Video: Sea horses
Activity: Interspecific interactions
Biology Labs On-Line: PopulationEcologyLab
Concept 53.2Dominant and keystone species exert strong controls on community structure
Transparencies
Figure 53.11 Which forest is more diverse?
Figure 53.12 Examples of terrestrial and marine food chains
Figure 53.13 An antarctic marine food web
Figure 53.14 Partial food web for the Chesapeake Bay estuary on the U.S. Atlantic coast
Figure 53.15 Test of the energetic hypothesis for the restriction of food chain length
Figure 53.16 Testing a keystone predator hypothesis
Figure 53.17 Sea otters as keystone predators in the North Pacific
Figure 53.19 Facilitation by black rush (Juncus gerardi) in New England salt marshes
Figure 53.20 Relationship between rainfall and herbaceous plant cover in a desert shrub community in Chile
Page 1171 Biomanipulation diagram
Student Media Resources
Activity: Food webs
Investigation: How are impacts on community diversity measured?
Concept 53.3Disturbance influences species diversity
and composition
Transparencies
Figure 53.23 A glacial retreat in southeastern Alaska
Figure 53.24 Changes in plant community structure and soil nitrogen during succession at Glacier Bay, Alaska
Student Media Resource
Activity: Primary succession
Concept 53.4Biogeographic factors affect community biodiversity
Transparencies
Figure 53.25 Energy, water, and species richness
Figure 53.26 Species-area curve for North American breeding birds
Figure 53.27 The equilibrium model of island biogeography
Figure 53.28 How does species richness relate to area?
Student Media Resource
Activity: Exploring island biogeography
Concept 53.5Contrasting views of community structure are the subject of continuing debate
Transparency
Figure 53.29 Testing the integrated and individualistic hypotheses of communities
Review
Transparency
Table 53.1 Interspecific interactions
For additional resources such as digital images and lecture outlines, go
to the Campbell Media Manager or the Instructor Resources section of www.campbellbiology.com.
Key Terms
aposematic coloration
Batesian mimicry
biomanipulation
biomass
bottom-up model
character displacement
coevolution
commensalism
community
competitive exclusion
cryptic coloration
disturbance
dominant species
dynamic stability hypothesis
ecological niche
ecological succession
ectoparasite
endoparasite
energetic hypothesis
evapotranspiration
facilitator
food chain
food web
herbivory
host
individualistic hypothesis
integrated hypothesis
intermediate disturbance hypothesis
interspecific interaction
interspecific competition
invasive species
keystone species
Müllerian mimicry
mutualism
nonequilibrium model
parasite
parasitism
parasitoidism
pathogen
predation
primary succession
redundancy model
relative abundance
resource partitioning
rivet model
secondary succession
species diversity
species richness
species-area curve
top-down model
trophic structure
Word Roots
crypto- 5 hidden, concealed (cryptic coloration: a type of camouflage that makes potential prey difficult to spot against its background)
ecto- 5 outer (ectoparasites: parasites that feed on the external surface of a host)
endo- 5 inner (endoparasites: parasites that live within a host)
herb- 5 grass; -vora 5 eat (herbivory: the consumption of plant material by an herbivore)
hetero- 5 other, different (heterogeneity: a measurement of biological diversity considering richness and relative abundance)
inter- 5 between (interspecific competition: competition for resources between plants, between animals, or between decomposers when resources are in short supply)
mutu- 5 reciprocal (mutualism: a symbiotic relationship in which both the host and the symbiont benefit)
##Instructor’s Guide for Campbell/Reece Biology, Seventh EditionChapter 53Community Ecology##Instructor’s Guide for Campbell/Reece Biology, Seventh EditionChapter 53Community Ecology##Instructor’s Guide for Campbell/Reece Biology, Seventh Edition